Nando's restaurant in Stratford, east London is unfortunately positioned. Sat plumb on a major junction, it has been surrounded by major roadworks all summer; it's noisy, dusty and not entirely suited to alfresco dining. The situation is perplexing Jammer, the grime producer and MC, so much so that he's been forced into freestyle: "Them man make so much noise though," he says. "It's like them cars when I'm sitting at Nando's."

Jammer likes to freestyle. Or at least he likes to come up with rhymes off the top of his head, which might be something different. We've met up to discuss the current flowering of the English MC, its variants and commonalities, over a plate of chicken and chips with a seemingly excessive side order of rice. It turns out he's of the mind that it's an MC's duty to engage with the environment they are in, hence the car rhymes.

"It's about what's happening," says Jammer, a thin man in his late 20s with long wispy dreads and a goatee to match. "I could make a lyric about whatever, it's just what I've seen and done. I might think, 'Them lads soft like Perinaise sauce', cause I'll have been to Nando's and Nando's is in my mind." The same applies to tone too. "If it's an energetic beat, I'm going to want to say something energetic with it. To create an energetic moment. Basically it's just about interacting. That's what MC-ing is. It's called mic controller. You interact and communicate with people; you make them smile, make them feel good. That's the art of it, communicating with people, bringing people together through music. That is what we do."

It's what he does, at least. This has been an epic year so far for British rappers. From number one singles (Tinie Tempah, Roll Deep, Dizzee Rascal), to an array of artist albums (including Example, Plan B, Klashnekoff) and a preposterously busy online scene where a site like Grimedaily can post at least 10 new videos every 24 hours. There has been a renaissance of the English MC, that much is clear It's just not entirely apparent quite what the English MC is.

Jammer has been involved in grime since its inception, watching it emerge from the London rave scene. "I used to go to the Stratford Rex and party at the Cool School nights", he says. "I was really into the jungle and the garage scene in the 1990s, that's where my influences come from."

There are similiarities between the stylings of a jungle or garage MC and a grime MC – high tempo, short lines, an emphasis on repeated words – but they are distinct crafts. Jammer attributes the difference, in the first instance, to a shift in diction. "Back in the day with the garage guys, they would more spit like 'bigbigyboowigawoobiga' doing funny voices," he says, through the medium of scat. "They didn't know how to get away from the tradition of mimicking American styles. That all changed with Wiley. I think Wiley was the main person to start spitting in a British accent, using British language. He made that connection."

So British dance music, plus Britons acting American, came together to form a distinctly British form of MCing. (To confuse things further Wiley, of course, is the grime pioneer who preferred to call the music he made by another name altogether – Eskibeat). But this stylistic crossbreeding has now stretched beyond grime.

Like Jammer, Professor Green grew up in east London, listening to jungle. "I was into music from really young, just from being out on my estate with my old 'uns", says Green, who was raised on Hackney's Northwold estate. "They were always listening to jungle, which was such a massive scene, especially in the East End. There were nights up in Tottenham and all the warehouse parties that I may or may not have snuck into. My nan used to play me Jason Donovan and Kylie Minogue records. That didn't have quite the same effect."

Green, real name Stephen Manderson, has a personable demeanour not entirely in keeping with the large tattoo that dominates his neck (it reads "lucky", a reference to having survived being stabbed in that very spot last year). He started out on jungle, but he graduated to hip-hop and made his name as a "battle" MC, competing with other rappers to deliver the best rhymes, with a bias towards florid insult.

"The first time I tried rapping I was 18. I was at my friend Core's house – he's now the executive producer on my album – and everyone was freestyling. I got put on the spot and did it as a joke. I went bright red in the face and never wanted to do it again. But everyone in the room was like, 'You can rap!' So I started battling as a freestyler. In about 2004, I got noticed by Mike Skinner at a jump-off battle at Brixton Academy. I then went on tour with him, and battled at every stop."

A deal with Skinner's label, the Beats, followed, only for the label to collapse, so Green's album never saw the light of day. "I took a lot from that time. I hadn't been making songs for that long and I was still pretty focused on the battling and stuff, so I learned a lot just looking at song structure and melody. It was a little disheartening, but I didn't really let it bring me down too far. I was pretty conscious of not wanting to become a bitter artist, because UK hip-hop is full of them. Full of people who feel like they deserve more than what they got and I didn't really want to become one of those people so I just worked harder."

Now Green is signed to Virgin and his debut album is at No 2 in the charts. It may not be an entirely unalloyed tale of triumph through hard work: Green is blond and handsome, and his big breakthrough hit, I Need You Tonight, is largely composed of the monster hook from the INXS song of the same name. That said, there is a wide menu of styles served up on his album: musically (dub, electro and, yes, old rave breaks) and also lyrically. His style switches regularly from an intricate hip-hop flow to something speedy and grimey, but it can also be hushed and melodic.

"I'm happy to flow over any tempo," says Green. "Grime is a massive scene in east London and I'm pretty sure we started it. I was never a grime artist, but I'm comfortable with grime, I've been on quite a few tracks with grime artists; grime artists have been on tracks with me. The thing is I'm not really bothered about the boundaries that much and I think the walls are falling down. For lack of a better term, it's urban music now, everyone kind of crosses the line."

To listen to artists like Tinie Tempah or Scorcher, from the grime scene but with flows that flip between tracks and even bars into something closer to hip-hop, you can see what Green means. It's something that applies equally, and excitingly, to the music they make. But while boundary-crossing might increasingly be the norm, it's not the rule. Some MCs know which niche they belong to and show no desire to change it.

Giggs is one such artist. A man who learned his craft while serving time in prison for possession of an unlicensed weapon, he has no problem describing his style. "In the street we just call it gangster music," he says, shrugging his shoulders. "In the jail days I was listening to DipSet and G-Unit, mostly them guys. When I came out, brothers then started listening to Jeezy and it was like, 'Rraaarr, this is my type of thing'. You know, like that slowed-down, greasy gangster shit."

Giggs's own music is quite clearly in the American gangster tradition, packed with tales of cocaine and gunfire, though you might not call it greasy; more clean or even clinical. His flow is slow, his tone flat and his rhymes plain ("It's like a factory the way we put the packs inside/I had a bad day, looking for a strap to buy" from Get Your Money Up). That, though, is the point.

"It's important for people to hear your lyrics. You can be the best rapper in the world but it's pointless if people don't know what the fuck you're talking about," he says, delivering every swearword with feeling. "You get people who say, 'He's not a good rapper and blah blah blah' because I don't get technical. But those rappers are like talking about the moon and the stars and all that shit, man. Fuck that."

Giggs is from Peckham in south London where he says only nerds listen to grime. The people he knows, some of whom form part of his own G-Unit-esque crew, SN1, listen to gangster music and nothing else. But what Giggs does share with Jammer and Green is a belief that his music should betray where it comes from. It may sound like it's been recorded with one ear on America, but the vocabulary and idioms are defiantly British.

"I'm not going to change what I'm saying because Americans might not understand it", he says. "I used to listen to Styles P and Jadakiss and they had songs about 'rolling in a hoopty'. That's probably what they call a rusty car or a banger or something. But the music was so sick I wanted to know. I want to make that kind of music. The music where you might not understand, but you're going to want to find out."

Braggadocio has always been a valuable commodity for a rapper to possess, but talking to these three artists, it is clear they all have confidence in common. Confidence in their own abilities, sure, but also in the sense that the music they are making is authentic and different from what preceded it. "I believe that someone like me will get a No 1 record," says Jammer, in between large mouthfuls of rice and Perinaise sauce. "I haven't given up on it, I haven't turned my back on it and it's only a matter of time before it happens. I'm willing to wait."

Jahmanji by Jammer is out now on Big Dada. A live Till I'm Dead by Professor Green is out now on Virgin. Let 'Em Have It by Giggs is out now on XL.